The present invention relates to a hydraulic lifting cylinder-piston unit, for example for leveling fluid-supported loads with stepping movements.
Hydraulic lifting cylinder-piston units of the above mentioned general type are known in the art. A known arrangement includes separately arranged structural groups of cylinder-piston units for a primary stroke, a secondary stroke and a leveling system, with a system of cylinder-piston units for a primary stroke and a secondary stroke as a unit, as well as a separately arranged leveling system.
The disadvantage of this solution is a high dead volume required by pipe and hose connections between the groups of cylinder-piston units and leveling cylinder-piston unit. A differential stroke during the reversing steps reaches up to 20% of the total stroke of the cylinder-piston unit, which for example during movement steps with highly located point of gravity of the load leads to an unfavorable dynamics (swinging motions),or in the event of horizontal arrangement an absolute position constant of the reference plane is not obtained.
A further disadvantage of the known solutions is a high material consumption and manufacturing expenses, as well as a significant space consumption. Also with the known solutions, no variable lifting displacements are possible.